The present invention relates to an inflator that generates a gas for inflating an air bag of a vehicle. More specifically, the present invention relates to an inflator having an advantage in that the gas can be ejected and supplied linearly in the axial direction of a bottle.
Inflators are gas generators that generate a gas for inflating air bags of vehicles. Inflators can be broadly divided into two groups: an inflator that ejects a high pressure gas contained in a container and supply it to an air bag (hybrid type and stored gas type), and an inflator that burns a gas generating agent (propellant) and generates a gas by utilizing a chemical reaction (combustion type).
An example of a stored gas type inflator is shown in FIG. 6. FIG. 6 is a sectional view schematically showing an inflator disclosed in Japanese Patent Application Publication No. 10-250525 as an example of a conventional stored gas type inflator.
With reference to the figure, an inflator 100 contains a bottle 101 that is filled with a high pressure gas. One end (the right end in the figure) 102 of the bottle 101 is closed and the other end (the left end in the figure) 103 of the bottle 101 is open. A sleeve 109 is connected to the open end 103 of the bottle 101 via an annular ring 106. An inner end of the ring 106, which forms an inside hole 106a, protrudes from the interior surface of the bottle 101 and the sleeve 109.
A burst disk 107 is attached to the ring 106 at the left side (the side facing the sleeve 109) thereof by welding, etc. The burst disk 107 is constructed of a steel plate having a thickness of approximately 0.3 mm. The burst disk 107 receives the filling pressure of the gas contained in the bottle 101 and swells toward the sleeve 109. In a normal state in which the inflator 100 is not activated, the bottle 101 is sealed by the burst disk 107.
A plurality of gas outlets 104, through which the high pressure gas is expelled when the inflator 100 is activated, is formed in the exterior surface of the sleeve 109. A housing 110 is attached to the sleeve 109 at the end (the left end in the figure) thereof. The housing 110 includes an initiator fixing member 110a, which is fit in the sleeve 109 at the end thereof, and a cylindrical portion 110b that protrudes from the initiator fixing member 110a. An initiator 112 is fixed inside the initiator fixing member 110a of the housing 110. A tip portion (at the right end) 112a of the initiator 112 is inserted beyond the initiator fixing member 110a into the cylindrical portion 110b. A terminal (at the left end) 112b of the initiator 112 is connected to a control unit via electric wires (not shown).
A piston 115 with a sharply pointed tip 115a is disposed inside the cylindrical portion 110b of the housing 110. A hole 115b is formed in the piston 115 at the rear end thereof, and the tip portion 112a of the initiator 112 is disposed in the hole 115b. A tip 110c of the cylindrical portion 110b of the housing 110 is separated from the burst disk 107 by a predetermined distance as shown in the figure.
An air bag (not shown) is attached to the inflator 100 in such a manner that the air bag is communicated via the gas outlets 104. In a normal situation, the gas contained in the bottle 101 is sealed by the burst disk (sealing plate) 107. When a vehicle collides, a sensor (not shown) is activated and the initiator 112 generates an air blast, so that the piston 115 is pushed to the right in the figure. The tip 115a of the piston 115 breaks the burst disk 107 at the midsection thereof, so that the entire body of the burst disk 107 is ruptured and opened widely. Then, the high pressure gas contained in the bottle 101 flows into the sleeve 109. The gas is ejected through the gas outlets 104 formed in the exterior surface of the sleeve 109 and supplied to the air bag.
In the above-described conventional inflator 100, the initiator 112, the piston 115, and the burst disk 107 are arranged such that the centers thereof are linearly arranged, and the piston 115 which is pushed by the air blast generated by the initiator 112 moves straight ahead and breaks the burst disk 107. However, in the above-described construction, the direction in which the gas flows into the sleeve 109 through the open end 103 of the bottle 101 (the horizontal direction in the figure) is approximately perpendicular to the direction in which the gas is ejected through the gas outlets 104 of the sleeve 109 into the air bag (the vertical direction in the figure). Accordingly, there is a problem in that the gas can not flow linearly and smoothly, and an additional component is necessary for changing the flowing direction of the gas.
In order to solve this problem, in Japanese Patent Application Publication No. 9-58394, a gas generator in which a gas can be ejected in the axial direction of a bottle from the closed end (the end opposite to the end closer to an initiator) toward the other is disclosed. However, in the gas generator of the above-described publication, there is a problem in that the size and the manufacturing cost thereof are increased since an additional large housing which contains the entire apparatus including the bottle is necessary.
In view of the above-described situation, an object of the present invention is to provide an inflator wherein a gas can be ejected and supplied linearly in the axial direction of a bottle without increasing the size and the manufacturing cost thereof.
To solve the problems described above, according to one aspect of the present invention, an inflator comprises a bottle with an opening and filled with a high pressure gas; a sealing plate which seals the opening of the bottle; an initiator which generates an air blast for providing driving force to break the sealing plate; a piston which is accelerated by the air blast generated by the initiator, and breaks the sealing plate; and a curved passage which guides the air blast generated by the initiator to the piston.
According to the present invention, the air blast generated by the initiator moves non-linearly through the curved passage, and then pushes and accelerates the piston. Then, the accelerated piston breaks the sealing plate, and the high pressure gas contained in the bottle is ejected. Since it is not necessary to dispose the initiator in the axial direction of the bottle, design flexibility can be increased. For example, the high pressure gas can be ejected and supplied linearly in the axial direction of the bottle.
According to another aspect of the present invention, an inflator comprises a bottle with an opening and filled with a high pressure gas; a sealing plate which seals the opening of the bottle; an initiator which generates an air blast for providing a driving force to break the sealing plate; and a piston which is accelerated by the air blast generated by the initiator and breaks the sealing plate. The bottle is a cylindrical shape, and the initiator is disposed in front of the opening of the bottle. A cylindrical diffuser provided with a gas outlet is connected to the bottle in the extending direction thereof. In addition, the initiator is attached to the circumferential surface of the diffuser and the gas outlet is formed in the diffuser at the end opposite to the end closer to the bottle.
According to the present invention, the initiator is disposed in front of the opening of the bottle and is attached to the circumferential surface of the diffuser. Thus, the initiator is not disposed in the direction in which the high pressure gas is ejected. Accordingly, the high pressure gas can be ejected and supplied linearly in the axial direction of the bottle. The high pressure gas which comes out from inside the bottle flows linearly through the diffuser and is ejected through the gas outlet formed in the diffuser at the end opposite to the end closer to the bottle.
An inflator of the present invention may further comprise a barrel having an inside hole which guides the piston, and the end surface of the barrel which is closer to the bottle may contact the sealing plate.
In such a case, the barrel supports a considerable percentage of the filling pressure of the gas contained in the bottle. Thus, even a relatively thin sealing plate can sustain a high pressure. After the sealing plate breaks, the gas flows through the space between the interior surface of the diffuser and the exterior surface of the barrel, and is then ejected through the gas outlet.